His doctoral dissertation, a "Mathematical Reformulation of the General Theory of International Trade" published by the University of Chicago Press in 1932, was considered a classic in its field.
Yntema was a pioneer contributor not only to the development of the Booth School of Business, but also to the whole field of quantitative analysis in finance during the 1920s, 1930s, and 1940s. His career furnished a strong bond between the theoretical and analytical facets of finance and its application to modern corporate management.
He served on the faculty of Chicago Booth from 1923 until 1949, when he joined the Ford Motor Credit Company. At Ford, he was vice president of finance and subsequently became chairman of the finance committee. Yntema was a Ford director and chairman of the board for two subsidiaries, Ford Motor Credit Company and America Road Insurance Company.
He was a life trustee of the University of Chicago, a member of the Council on Chicago Booth, a professional lecturer in business policy at Chicago Booth, a visiting professor at Oakland University, a trustee of the Committee on Economic Development, and a chairman of the National Bureau of Economic Research.
The Theodore O. Yntema Professorship at Chicago Booth was established in 1973.